The alleged murder of a professional surfer by five youths in one of California's most exclusive beachfront enclaves has left a community reeling and pondering the dark side of its young residents' privileged lives.

Emery Kauanui Jr, a 24-year-old Hawaii-born surfer, died after he was beaten outside his mother's house in La Jolla, a coastal paradise of multimillion dollar homes just north of San Diego.

Five young men have been charged with his death. The men were childhood friends who grew up together, played on their school sports teams and socialised as a group in La Jolla's bars.

Then, it is alleged, they formed a gang, calling themselves the Bird Rock Bandits, named after one of town's neighbourhoods. They also adopted behaviour more common to traditional street-gang heartlands such as South Central Los Angeles: intimidation and violence.

Authorities say the killing was the culmination of a bubbling culture of violence. It has left residents examining which aspects of life in the well-heeled town of 50,000 could possibly foster such behaviour.

And it has drawn comparisons to other alleged gang activity by youths in affluent areas.

Earlier this year members of a gang from suburban Carlsbad dubbed the Shadow Crew pleaded guilty to charges relating to a plot to kidnap and murder twin brothers.

The gang, which reportedly modelled itself on The Sopranos, held weekly meetings at its ringleader's million-dollar home, according to police.

Its members included as US Navy sailor, a scoutmaster and a personal trainer and businessman. After the group failed to find the twins they were targeting, they reportedly went out for sushi instead.

In Murietta, Riverside County, another group of middle-class men calling themselves the Fight Club assaulted a man at a birthday party. Eleven young men later pleaded guilty to charges ranging from assault and arson to burglary. Their raids included the theft of gym equipment, flat-screen televisions and a case of designer sunglasses.

Investigators say the death of Mr Kauanui, who was assaulted in May and died four days later in hospital, is just the latest incident in a worrying trend in which rich, young men adopt gangland lifestyles, possibly out of boredom or for the kudos.

Defence lawyers and relatives of the accused, however, say prosecutors are introducing gang-related charges to these cases purely in a bid to secure tougher sentences and in reality, the groups are more akin to social clubs than street gangs.

In Mr Kauanui's case, a bar fight preceded the brawl that led to his death. Seth Cravens, 21, has been charged with murder while four other 20-somethings face gang-related charged connected to the death.

Prosecutors say the group followed the surfer home and attacked him. They also allege Cravens had a hoard of gang-style paraphernalia including notebooks with Bird Rock Bandits and Nazi symbols "such as lightning bolts and swastikas".

All the accused, including a star college football player, have pleaded not guilty. Their lawyers say the charges are excessive and the death was accidental.

"This wasn't a killing," Alan Spears, Cravens' lawyer, told the Los Angeles Times. "It was a fistfight."

Whatever the details, the incident has shaken a community known for its serene, laid-back life of plenty and pleasure.

"I think this has been La Jolla's dirty little secret," David Ponsford, the high school's football coach, told the Los Angeles Times. "No one has wanted to address it."

Anne Cleveland, the president of the Town Council, told the paper more could have been done. "These kids had been doing this since high school," she said.

"It was hidden in plain sight. That's the crux of the tragedy. It could have been avoided if people had spoken up about it more vociferously. As a result, six young lives are basically over."

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